Meters which measure and register the accumulated flow of fluids by volume or by mass are well known. Likewise, various devices which measure the transmission rate of mechanical and electrical energy are in use. For registering the accumulated electrical energy flow, integrating watt-meters--watt-hour meters--are commonplace items. The present invention relates to means for measuring the accumulated flow of transported thermal energy for use in a manner similar to that of an electrical watt-hour meter, but associated with the volumetric flow of fluid subjected to a temperature change.
Such a thermal energy meter is a desirable device. Fluid flow meters such as water meters are widely employed to measure the transmission of water and to enable accurate billing or accounting to be rendered. In many cases, heated or chilled water is being transmitted, and in such cases the value of the thermal energy involved may be comparable to or may exceed the value of the water itself. A thermal energy meter is especially valuable when the fluid is part of a closed system and serves only as a medium for heat transmission or exchange. In this case, the only net flow is the flow of thermal energy itself, and the energy is the only extensive quantity which can be meaningfully metered.